Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758752AbbEFDjP (ORCPT ); Tue, 5 May 2015 23:39:15 -0400 Received: from g2t2352.austin.hp.com ([15.217.128.51]:54235 "EHLO g2t2352.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757456AbbEFDjN (ORCPT ); Tue, 5 May 2015 23:39:13 -0400 Message-ID: <55498CDD.7010403@hp.com> Date: Tue, 05 May 2015 23:39:09 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12 MIME-Version: 1.0 To: Mel Gorman CC: Andrew Morton , Nathan Zimmer , Dave Hansen , Scott Norton , Daniel J Blueman , Linux-MM , LKML Subject: Re: [PATCH 0/13] Parallel struct page initialisation v4 References: <1430231830-7702-1-git-send-email-mgorman@suse.de> <554030D1.8080509@hp.com> <5543F802.9090504@hp.com> <554415B1.2050702@hp.com> <20150504143046.9404c572486caf71bdef0676@linux-foundation.org> <20150505104514.GC2462@suse.de> <5548CBE8.5090203@hp.com> <20150505143102.GD2462@suse.de> <5548DB38.6080402@hp.com> In-Reply-To: <5548DB38.6080402@hp.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5602 Lines: 136 On 05/05/2015 11:01 AM, Waiman Long wrote: > On 05/05/2015 10:31 AM, Mel Gorman wrote: >> On Tue, May 05, 2015 at 09:55:52AM -0400, Waiman Long wrote: >>> On 05/05/2015 06:45 AM, Mel Gorman wrote: >>>> On Mon, May 04, 2015 at 02:30:46PM -0700, Andrew Morton wrote: >>>>>> Before the patch, the boot time from elilo prompt to ssh login >>>>>> was 694s. >>>>>> After the patch, the boot up time was 346s, a saving of 348s >>>>>> (about 50%). >>>>> Having to guesstimate the amount of memory which is needed for a >>>>> successful boot will be painful. Any number we choose will be wrong >>>>> 99% of the time. >>>>> >>>>> If the kswapd threads have started, all we need to do is to wait: >>>>> take >>>>> a little nap in the allocator's page==NULL slowpath. >>>>> >>>>> I'm not seeing any reason why we can't start kswapd much earlier - >>>>> right at the start of do_basic_setup()? >>>> It doesn't even have to be kswapd, it just should be a thread >>>> pinned to >>>> a done. The difficulty is that dealing with the system hashes means >>>> the >>>> initialisation has to happen before vfs_caches_init_early() when >>>> there is >>>> no scheduler. Those allocations could be delayed further but then >>>> there is >>>> the possibility that the allocations would not be contiguous and >>>> they'd >>>> have to rely on CMA to make the attempt. That potentially alters the >>>> performance of the large system hashes at run time. >>>> >>>> We can scale the amount initialised with memory sizes relatively easy. >>>> This boots on the same 1TB machine I was testing before but that is >>>> hardly a surprise. >>>> >>>> ---8<--- >>>> mm: meminit: Take into account that large system caches scale >>>> linearly with memory >>>> >>>> Waiman Long reported a 24TB machine triggered an OOM as parallel >>>> memory >>>> initialisation deferred too much memory for initialisation. The likely >>>> consumer of this memory was large system hashes that scale with memory >>>> size. This patch initialises at least 2G per node but scales the >>>> amount >>>> initialised for larger systems. >>>> >>>> Signed-off-by: Mel Gorman >>>> --- >>>> mm/page_alloc.c | 15 +++++++++++++-- >>>> 1 file changed, 13 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 598f78d6544c..f7cc6c9fb909 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -266,15 +266,16 @@ static inline bool >>>> early_page_nid_uninitialised(unsigned long pfn, int nid) >>>> */ >>>> static inline bool update_defer_init(pg_data_t *pgdat, >>>> unsigned long pfn, unsigned long zone_end, >>>> + unsigned long max_initialise, >>>> unsigned long *nr_initialised) >>>> { >>>> /* Always populate low zones for address-contrained >>>> allocations */ >>>> if (zone_end< pgdat_end_pfn(pgdat)) >>>> return true; >>>> >>>> - /* Initialise at least 2G of the highest zone */ >>>> + /* Initialise at least the requested amount in the highest >>>> zone */ >>>> (*nr_initialised)++; >>>> - if (*nr_initialised> (2UL<< (30 - PAGE_SHIFT))&& >>>> + if ((*nr_initialised> max_initialise)&& >>>> (pfn& (PAGES_PER_SECTION - 1)) == 0) { >>>> pgdat->first_deferred_pfn = pfn; >>>> return false; >>>> @@ -299,6 +300,7 @@ static inline bool >>>> early_page_nid_uninitialised(unsigned long pfn, int nid) >>>> >>>> static inline bool update_defer_init(pg_data_t *pgdat, >>>> unsigned long pfn, unsigned long zone_end, >>>> + unsigned long max_initialise, >>>> unsigned long *nr_initialised) >>>> { >>>> return true; >>>> @@ -4457,11 +4459,19 @@ void __meminit memmap_init_zone(unsigned >>>> long size, int nid, unsigned long zone, >>>> unsigned long end_pfn = start_pfn + size; >>>> unsigned long pfn; >>>> struct zone *z; >>>> + unsigned long max_initialise; >>>> unsigned long nr_initialised = 0; >>>> >>>> if (highest_memmap_pfn< end_pfn - 1) >>>> highest_memmap_pfn = end_pfn - 1; >>>> >>>> + /* >>>> + * Initialise at least 2G of a node but also take into account >>>> that >>>> + * two large system hashes that can take up an 8th of memory. >>>> + */ >>>> + max_initialise = min(2UL<< (30 - PAGE_SHIFT), >>>> + (pgdat->node_spanned_pages>> 3)); >>>> + >>> I think you may be pre-allocating too much memory here. On the 24-TB >>> machine, the size of the dentry and inode hash tables were 16G each. >>> So the ratio is about is about 32G/24T = 0.13%. I think a shift >>> factor of (>> 8) which is about 0.39% should be more than enough. >> I was taking the most pessimistic value possible to match where those >> hashes currently get allocated from so that the locality does not change >> after the series is applied. Can you try both (>> 3) and (>> 8) and >> see >> do both work and if so, what the timing is? > > Sure. I will try both and get you the results, hopefully by tomorrow > at the latest. > With the modified patch, both (>>3) and (>>8) worked without any problem. The bootup times are: 1. Unpatch 4.0 kernel - 694s 2. Patch kernel with 4G/node - 346s 3. Patch kernel with (>>3) - 389s 4. Patch kernel with (>>8) - 353s Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/